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  • The Scorching Summer of 2015

  • Friday, 25th September 2015

The U.S. National Oceanic and Atmospheric Administration recently announced that the globally averaged temperature over land and ocean surfaces in summer (June to August) 2015 was the highest ever recorded for the globe since 1880[1].

Hong Kong also experienced the hottest summer ever since records began in 1884 with the mean temperature for June to August 2015 reaching 29.4 degrees, breaking the previous record of 29.3 degrees set not so long ago last year.

June 2015 was actually the hottest June on record (Table 1). Under the subsidence effect associated with Typhoon Soudelor, the temperature at the Hong Kong Observatory soared to a record-breaking 36.3 degrees on 8 August 2015, beating the previous extreme of 36.1 degrees set in 1990[2]. More details on the record-breaking temperatures this summer are summarized in Table 2.

Table 1

Table 2

In fact, under the combined influence of global warming and urbanization development, there is a very significant long-term rising trend in the summer mean temperatures in Hong Kong (Figure 1). Record-breaking temperatures are evidently becoming more frequent, with four of the six hottest summers occurring within the past seven years (Table 3). Looking forward, if we fail to reduce greenhouse gas emission as soon as possible, the latest climate projections suggest that under a high emission scenario, the mean temperature in Hong Kong is expected to rise 1.5 - 3.0oC by the mid-21st century (2051-2060) as compared to the 1986-2005 average[3]. This implies that very hot days, hot nights and extreme temperature records in future summers would only keep increasing, bringing negative impacts to our living conditions, especially for the underprivileged who have to stay in congested and poorly ventilated environment. The very hot conditions will also mean enhanced air-conditioning demand and hence more energy consumption. This will create a vicious negative feedback cycle with a profound implication of adverse social and economic consequences in the long run.

Figure 1

Figure 1 - Long Term Trend of Summer Mean Temperature (June - August) recorded at the Hong Kong Observatory

Table 3

K W Li and K M Leung

References :

[1] NOAA Global Analysis - August 2015

[2] Record-breaking high temperature

[3] Hong Kong temperature projections

  • A Visit to Mr. and Mrs. Peacock

  • Friday, 11th September 2015

Shortly after the end of the Second World War, he learnt of the state of affairs around the world from his relative, and decided to give up his position as an engineer in a ceramics plant in England. He travelled to Southeast Asia by himself, and on arriving in Hong Kong, he joined the Observatory. Before long, he started a family and settled down here. From then on, he witnessed decades of weather and history in this small territory, half a globe away from where he grew up. It was only after retirement that he returned to his homeland.

He is Mr. John Peacock, a former Director of the Observatory. He retired in 1984 as the last Director coming from England, after 34 years of service at the Observatory. His family then resettled in the southwestern part of England, and has been living in ethereal calm ever since.

This summer, I was on a short course in Oxford, England. Having liaised through the current Director Mr. CM Shun, I together with another colleague, PW Lau, who was receiving training in meteorology in Exeter, visited Mr. and Mrs. Peacock at their home on a Sunday. We had the pleasure of having the classic English tea prepared by Mrs. Peacock while chatting through a sunny and joyful afternoon.

Mr. and Mrs. Peacock's home is in Somerset, about half-an-hour's drive from Bath, the nearest city. The small village is sparsely populated with plenty of fresh air. Their house is located in a picturesque site, with a panoramic view of grassland all around. The ex-Director has planted a great variety of flowers and trees in his garden. Still a scientist at heart, he has carefully recorded every single plant in detail. Although over 80 years old, he walked fast and could easily pick up steel-made garden tools, clearly demonstrating the benefits of gardening in keeping the body fit.

Figure 1

Figure 1      Grassland beyond Mr. Peacock's back garden.

Figure 2

Figure 2      Group photo in the back garden. From left to right: Diane Peacock, PW Lau, WC Woo, John Peacock.

Mr. Peacock hoisted the No. 10 Hurricane Signal four times as director or acting director, probably the director of the recent generations who hoisted the largest number of the No. 10 Hurricane Signal (Note 1). He said the greatest challenge in those days was primarily the lack of observation data. There were only a few meteorological stations and reporting ships, and even no meteorological satellites in the early days. It was therefore rather difficult to forecast the weather at those times. Based on the level of technology and social developments back then, considerations in hoisting typhoon signals were entirely different from those of the modern days.

He further recalled that there were a lot of manual routines in the past. Take replicating weather charts as an example. In the old days, staff had to employ a technique known as lithography (Note 2), by laying an analysed weather chart on a smooth limestone, pouring acid onto the limestone followed by a solution, and subsequently copying a blank chart over.

Figure 3

Figure 3      A weather chart of 23 November 1983 given to us by Mr. Peacock,
showing clearly the hand-written pressure values.

Mr. Peacock had safeguarded plenty of precious photographs, some of which even had name lists attached. We seized the opportunity and asked him to digitise part of his collection, in order to enrich the heritage list of the Observatory.

Figure 4

Figure 4      A group photo taken in the 1950s, well-preserved by Mr. Peacock.

Although decades had passed, Mr. Peacock still remembered vividly the Observatory's first atomic clock (Note 3). He also recalled an occasion in which numerous fishermen approached Hong Kong from the coast of Guangdong due to a rumour of an impending earthquake and, as a result, the Observatory had to refute it. Mr. and Mrs. Peacock further shared with us a personal sighting of an unidentified flying object. We were so immersed in the stories that we almost forgot to leave.

Before our departure, Mr. Peacock referred to a story of him successfully solving an equation as an engineer, and reminded us that: "We should be proud of our achievements". Indeed, we should all be proud of our work and missions.

WC Woo and Stephen PW Lau

[Note: Mrs. Diane Peacock sadly passed away in July 2015. We express our deepest condolences to Mr. Peacock and his family.]


1.   Please refer to Some Collective Memories of the Observatory - Visiting Ex-Director John Peacock.

2.   "Lithography" originates from the ancient Greek word "lithos" meaning "stone".

3.   Please refer to History of Hong Kong Time Service.

  • Can A Quiet Sun Halt Warming on Earth?

  • Wednesday, 19th August 2015

Whenever there are reports of predicted decrease in solar activity, climate change deniers will seize the opportunity to exaggerate the effect of the solar activity on the Earth's temperature change. An oft-quoted piece of misinformation spread by the deniers is the return of ice age due to weakening solar activity. So to what extent does the solar activity contribute to variations in the Earth's temperature?

Satellite-based instruments have been measuring the amount of solar energy reaching the top of the atmosphere (also known as total solar irradiance, or TSI in short) since the late 1970s. The average value of TSI is found to be about 1361 Wm-2. While solar activity follows a cycle of roughly 11 years, the average fluctuation of TSI over the past several solar cycles is only about 0.1%. For pre-satellite times, TSI variations have to be estimated from sunspot numbers or radioisotope analysis of polar ice and tree rings. Solar activity was very low during the period of 1645-1715, also known as the Maunder Minimum. The estimated difference in TSI values between the Maunder Minimum and the present day is also in the order of 0.1%.

As simulated by the US National Aeronautics and Space Administration (NASA) state-of-the-art climate model, changes in terms of global surface temperature anomaly due to solar activity were found to be generally within plus or minus 0.1oC over the period of 1880-2005 (blue line in Figure 1), a rather insignificant contribution as compared against the fast-growing influence of human-caused increase in greenhouse gases (red line in Figure 1). Similar conclusions were drawn in a recent climate model study conducted by the scientists at the UK Meteorological Office[1] to simulate conditions for the second half of the 21st century under the high greenhouse gas concentration scenario and incorporating a decreasing solar output down to the Maunder Minimum levels. It was found that the cooling effect arising from reduced solar output was a mere 0.1oC. To put this into context, we are talking about several degrees of temperature increase by the end of the 21st century under the high greenhouse gas concentration scenario according to projections (Figure 2) in the Fifth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC). As such, to rely on the Sun to give us a helping hand appears to be just wishful thinking!

Figure 1

Figure 1      Simulated global surface temperature anomaly (relative to the 1880-1910 average)
due to solar activity and greenhouse gases. (data source: NASA)

Figure 2

Figure 2      Projected global average surface temperature change (relative to the average of 1986-2005) under
the high (in red) and low (in blue) greenhouse gas concentration scenarios in the 21st century,
with the colour-shaded regions indicating the respective range of uncertainty. (Source: IPCC)

S M Lee and F C Sham


[1] Scientists show a decline in solar activity could not halt global warming